1. Field of the Invention
The invention relates to the encapsulation of hydrophilic compounds, and more specifically to a method of preparing particles having a hydrophilic core coated with a hydrophobic polymeric layer.
The fields of use of the present invention particularly include the paper industry, the textile industry, printing, the pharmaceutical industry, or plastics engineering.
2. Description of Related Art
The protection by encapsulation of chemical compounds and particularly of hydrophilic compounds enables to control or to modify the properties thereof It is thus possible to predetermine the conditions of release of an active principle, to lengthen the lifetime of a product by protecting it from external elements, but also to improve the dispersibility of a compound.
For example, in the paper industry, except for cellulose fibers, most of the components (such as colorants, optical brighteners or active principles) used are water-soluble. Since paper manufacturing processes are essentially carried out in an aqueous environment, it is thus particularly difficult to incorporate water-soluble compounds. Indeed, the fibers forming the sheet of paper can only partially retain such water-soluble compounds. Accordingly, this generates considerable losses and requires a system of continuous recirculation of aqueous solutions of optical brighteners and colorants.
Further, at the end of the impregnation, waste waters contain a significant amount of optical brighteners or of colorants and thus should be submitted to a special new treatment.
On the other hand, it is almost impossible to accurately control the quantity of optical brighteners or of colorants impregnated on paper. Whitenesses or colorant shades may thus differ from one impregnation to another.
To overcome such issues of solubility and of lack of interaction between optical brighteners and fibers, new less water-soluble agents have been developed. Although it is relatively satisfactory, such a solution has the disadvantage of limiting the range of selectable optical brighteners, which are further more expensive than fully water-soluble agents.
Accordingly, there is a technological need for a method enabling to decrease, or even to suppress losses of optical brighteners and of colorants, as well as to accurately know the deposited quantities.
The present invention enables to solve prior art problems particularly relative to the retention of conventional optical brighteners or colorants in paper manufacturing processes. The method developed by the Applicant enables to prepare particles by coating of hydrophilic compounds with a hydrophobic polymeric layer.